This invention pertains to a method for producing hydrogenated silicon oxycarbide (H:SiOC) films having low dielectric constant. The method comprises reacting a methyl-containing silane in a controlled oxygen environment using plasma enhanced or ozone assisted chemical vapor deposition to produce the films. The resulting films are useful in the formation of semiconductor devices.
The use of chemical vapor deposition (CVD) to produce SiO2, SiNC or SiC thin films on semiconductor devices from silicon-containing materials is well known in the art. Chemical vapor deposition processes typically comprise introducing the gaseous silicon-containing material and a reactive gas into a reaction chamber containing the semiconductor substrate. An energy source such as thermal or plasma induces the reaction between the silicon-containing material and reactive gas thereby resulting in the deposition of the thin film of SiO2, SiNC or SiC on the semiconductor device. Plasma enhanced chemical vapor deposition (PECVD) is typically carried out at low temperatures ( less than 500xc2x0 C.) thereby making PECVD a suitable means for producing dielectric and passivation films on semiconductor devices. Silicon-containing materials include silane (SiH4), tetraethyl orthosilicate (TEOS), silacyclobutanes, and alkylsilanes such as trimethylsilane.
The use of methyl-containing silanes to produce silicon dioxide (SiO2), amorphous SiNC and silicon carbide (SiC) films by chemical vapor deposition is known in the art. For example, U.S. Pat. No. 5,465,680 to Loboda discloses a method for making crystalline SiC films. The method comprises heating the substrate 600xc2x0 C. to 1000xc2x0 C. and thereafter exposing the substrate to trimethylsilane in a standard chemical vapor deposition process. EP Patent Application No. 0 774 533 to Loboda discloses a method of making SiO2 coatings from the CVD of a reactive gas mixture comprising an organosilicon material and an oxygen source. EP Patent Application No. 0771 886 to Loboda discloses a method of making SiNC coating from the CVD of a reactive gas mixture comprising an organosilicon material and a nitrogen source.
As semiconductor device structures become increasingly smaller the dielectric constant as well as the integrity of the film become important. Films produced by known CVD processes have high dielectric constants (i.e. 3.8 or greater). Therefore there is a need for processes and materials that result in low dielectric constant films. A new deposition processes known as Low-k Flowfill(copyright), produces films having a dielectric constant of  less than 3.0. This method uses a chemical vapor deposition reaction between methylsilane and hydrogen peroxide to produce a methyl doped silicon oxide film (See S. McClatchie, K. Beekmann, A. Kiermasz; Low Dielectric Constant Oxide Films Deposited Using CVD Techniques, 1988 DUMIC Conference Proceedings, 2/98, p. 311-318). However, this process requires a non standard CVD system, the use of a lower stability oxygen source (hydrogen peroxide) and generates water as a by-product which can be undesirable in semiconductor devices.
It is therefore an object of this invention to provide a method for producing low dielectric constant thin films of hydrogenated silicon oxycarbide by chemical vapor deposition.
This invention pertains to a method of producing thin films of hydrogenated silicon oxycarbide (H:SiOC) having low dielectric constants on substrates, preferably semiconductor devices. The method comprises the plasma enhanced or ozone enhanced chemical vapor deposition of a reaction mixture comprising an methyl-containing silane and an oxygen providing gas. By controlling the amount of oxygen available during the reaction/deposition process a film comprising hydrogen, silicon, carbon and oxygen is produced. These films typically have a dielectric constant of 3.6 or less and are particularly suited as interlayer dielectrics.